Phase shift mask and manufacturing method thereof and exposure method using phase shift mask comprising a semitransparent region

ABSTRACT

A second light transmit portion of a phase shift mask is formed of a molybdenum silicide nitride oxide or a molybdenum silicide oxide a chromium nitride oxide, or a chromium oxide, or a chromium carbide nitride oxide film converting a phase of transmitted exposure light by 180° and having the transmittance of 5-40%. In the manufacturing method of the second light transmit portion, a molybdenum silicide nitride oxide film or a molybdenum silicide oxide film a chromium nitride oxide film, or a chromium oxide film, or a carbide nitride oxide film is formed by a sputtering method. Consequently, with a conventional sputtering apparatus, the second light transmit portion can be formed, and additionally, etching process of the phase shifter portion is required only once, so that probabilities of defects and errors in the manufacturing process can be decreased.

This application is a division of application Ser. No. 08/155,370 filedNov. 22, 1993 now U.S. Pat. No. 5,474,864.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to phase shift masks, andparticularly to a structure of a phase shift mask of attenuation typeattenuating light intensity, and a method of manufacturing the same. Thepresent invention further relates to an exposure method using the phaseshift mask.

2. Description of the Background Art

Recently, high integration and miniaturization of a semiconductorintegrated circuit has been remarkably advanced, involvingminiaturization of a circuit pattern formed on a semiconductor substrate(hereinafter referred to simply as a wafer).

In particular, a photolithography technique is well known as a basictechnique in pattern formation. Although various developments andimprovements have been made, miniaturization of a pattern still keeps onadvancing, and a demand for enhancement of a pattern resolution has beenincreasing.

In general, a resolution limit R (nm) in a photolithography techniqueusing a reduction exposure method is described by the following:

    R=k.sub.1 ·λ/(NA)                          (1)

where λ is a wavelength (nm)of light to be used, NA is a numericalaperture of a lens, and k₁ is a constant which depends on a resistprocess.

As can be seen from the above expression, in order to enhance theresolution limit, k₁ and λ should be made smaller, and NA should be madelarger. That is, the wavelength should be decreased, and NA should beincreased, with the constant which depends on a resist process madesmaller.

However, improvement of a light source and a lens is technicallydifficult. In addition, a depth of focus δ (δ=k₂ ·λ/(NA)²) of light ismade smaller by decreasing the wavelength and increasing NA, whichrather leads to deterioration in the resolution.

Description will now be made of a cross section of a mask, an electricfield of exposure light on the mask, and light intensity on a wafer inusing a conventional photomask, with reference to FIGS. 31A, 31B, 31C.

First, the cross sectional structure of the mask will be described withreference to FIG. 31A. A metal mask pattern 2 of chromium or the like isformed on a glass substrate 1.

Referring to FIG. 31B, an electric field is generated along the maskpattern. Referring to FIG. 31C, however, light beams passing through themask intensify each other at an overlaid portion of the light beamscaused by light diffraction and interference. Consequently, thedifference in the light intensity on the wafer becomes smaller, so thatthe resolution is deteriorated.

A phase shift exposure method with a phase shift mask has been proposedfor solving this problem, for example, in Japanese Patent Laying-OpenNos. 57-62052 and 58-173744.

The phase shift exposure method with a phase shift mask disclosed inJapanese Patent Laying-Open No. 58-173744 will now be described withreference to FIGS. 32A, 32B, 32C.

FIG. 32A shows a cross section of the phase shift mask. FIG. 32B showsan electric field on the mask. FIG. 32C shows light intensity on awafer.

First, referring to FIG. 32A, a phase shifter 6b of a transparentinsulation film such as a silicon oxide film is provided at every otheraperture portion 6a of a chromium mask pattern 2 formed on a glasssubstrate 1 to form a phase shift mask.

Referring to FIG. 32B, the electric field of a light beam passingthrough phase shifter 6b of the phase shift mask is inverted by 180°.

Therefore, the light beams transmitted through aperture portion 6a andthrough phase shifter 6b cancel each other on an overlaid portionthereof caused by a light interference effect. Consequently, as shown inFIG. 32C, the difference in the light intensity on the wafer issufficient for enhancing the resolution.

Although the aforementioned phase shift mask is very effective for aperiodical pattern such as lines and spaces, it cannot be set to anarbitrary pattern because complexity of the pattern causes greatdifficulty in arrangement of a phase shifter and the like.

As a phase shift mask solving the above problem, a phase shift mask ofattenuation type is disclosed, for example, in JJAP Series 5 Proc. of1991 Intern. Microprocess Conference pp. 3-9 and Japanese PatentLaying-Open No. 4-136854. Description will hereinafter be made of thephase shift mask of attenuation type disclosed in Japanese PatentLaying-Open No. 4-136854.

FIG. 33A is a cross section of the phase shift mask of attenuation type.FIG. 33B shows an electric field on the mask. FIG. 33C shows lightintensity on a wafer.

Referring to FIG. 33A, the structure of a phase shift mask 100 includesa quartz substrate 1 transmitting exposure light, and a phase shiftpattern 30 having a prescribed exposure pattern including a first lighttransmit portion 10 formed on a main surface of quartz substrate 1 andhaving the main surface exposed, and a second light transmit portion 20converting a phase of transmitted exposure light by 180° with respect tothe phase of exposure light transmitted through first light transmitportion 10.

Second light transmit portion 20 has a double layer structure includinga chromium layer 2 having the transmittance of 5-40% for exposure light,and a shifter layer 3 converting a phase of exposure light transmittedtherethrough by 180° with respect to that of exposure light transmittedthrough light transmit portion 10.

The electric field on the mask, of exposure light passing through phaseshift mask 100 having the above-described structure is as shown in FIG.33B. The light intensity on the wafer has its phase inverted at an edgeof the exposure pattern as shown in FIG. 33C.

The light intensity at an edge of the exposure pattern, therefore, isinvariably 0, as shown in the figure, so that the difference in theelectric field on light transmit portion 10 and phase shifter portion 20of the exposure pattern is sufficient for high resolution.

It should be noticed that the transmittance of second light transmitportion 20 for exposure light is set to 5-40% in the above method, forthe purpose of adjusting the thickness of the resist film afterdevelopment thereof by the transmittance, as shown in FIG. 30, so as toadapt the exposure amount appropriately for lithography.

Description will now be made of a method of manufacturing phase shiftmask 100. FIGS. 35 to 39 are cross sectional views showing themanufacturing steps according to the cross section of phase shift mask100 shown in FIG. 33.

Referring to FIG. 35, chromium film 2 having the exposure lighttransmittance of 5-40% and the thickness of 50-200Å, approximately, isformed on glass substrate 1. Thereafter, on chromium film 2 formed isSiO₂ film 3 of a prescribed thickness having the phase of exposure lightpassing therethrough converted by 180°. An electron beam resist film 5is formed on SiO₂ film 3.

Referring to FIG. 36, a predetermined portion-of electron beam resistfilm 5 is exposed to electron beams and developed to form a resist 5having a desired pattern.

Referring to FIG. 37, with resist film 2 as a mask, the SiO₂ film isetched using a gas of the CHF₃ family. Referring to FIG. 38, chromiumfilm 2 is subjected to wet etching with resist film 5 and SiO₂ film 5 asa mask.

Referring to FIG. 39, phase shift mask 100 is completed by removingresist film 5.

In the above conventional technique, however, second light transmitportion 20 has a double layer structure including chromium film 2 forcontrolling the transmittance and SiO₂ film 3 for controlling the phasedifference. This structure, therefore, requires devices and processrespectively for formation of a chromium film and an SiO₂ film.

In addition, the chromium film and the SiO₂ film must be etchedseparately with different etching agents, resulting in numerous steps ofthe process, and thus leading to higher probabilities of defects and ofprocess errors in the pattern dimension.

Referring to FIG. 40, when a remaining defect (opaque defect) 50 and apinhole defect (clear defect) 51 should occur in the phase shift maskpattern, repairing methods respectively applicable to a chromium filmand an SiO₂ film will be required for repairing the defect. Aconventional repairing method, therefore., cannot be employed.

Referring to FIG. 41, according to an exposure method using theabove-described phase shift mask 100, the film thickness of a secondlight transmit portion 20 of phase shift mask 100 is approximately 3050Åto 4200Å, which is relatively large. Therefore, as shown in the figure,oblique exposure light out of exposure light from an exposure lightsource has its phase not reliably converted by 180° even if it transmitsthrough second light transmit portion 20 of phase shift mask 100.Exposure light having a different phase is produced.

SUMMARY OF THE INVENTION

One object of the present invention is to simplify manufacturing processof a phase shift mask, so as to provide a phase shift mask of highquality.

Another object of the present invention is to provide a manufacturingmethod of a phase shift mask having process simplified.

A still another object of the present invention is to provide anexposure method using a phase shift mask, which can prevent exposurefailure and improve the yield in the manufacturing steps of asemiconductor device.

In one aspect of the present invention, the phase shift mask includes asubstrate transmitting exposure light, and a phase shift pattern formedon a main surface of the substrate. The phase shift pattern includes afirst light transmit portion having the substrate exposed, and a secondlight transmit portion of a single material having a phase oftransmitted exposure light converted by 180° with respect to the phaseof exposure light transmitted through the first light transmit portion,and having the transmittance of 5-40%.

The second light transmit portion is preferably formed of a singlematerial selected from the group consisting of an oxide and a nitrideoxide of metal, and an oxide and a nitride oxide of metal silicide.

The second light transmit portion is preferably formed of a singlematerial selected from the group consisting of an oxide, a nitrideoxide, and a carbide nitride oxide of chromium, and an oxide and anitride oxide of molybdenum silicide.

The second light transmit portion preferably has the transmittancecontrolled through oxygen or nitrogen included therein, and the phasedifference controlled through the thickness thereof.

In accordance with the present invention, the method of manufacturing aphase shift mask includes the following steps.

A phase shifter film of a prescribed thickness having a phase oftransmitted exposure light converted by 180°, and having thetransmittance of 5-40% is formed on a substrate transmitting exposurelight by a sputtering method. A resist film of a prescribed pattern isformed on the phase shifter film.

With the resist film as a mask, the phase shifter film is etched by adry etching method, so that a first light transmit portion having thesubstrate exposed and a second light transmit portion formed of thephase shifter film are formed.

The step of forming the phase shifter film preferably includes the stepof forming a molybdenum silicide oxide film with a molybdenum silicidetarget in a mixed gas atmosphere of argon and oxygen.

The mixed gas preferably includes 65-92% argon gas, and an oxygen gas ofthe remaining percent by volume. The step of forming the phase shifterfilm preferably includes the step of forming a molybdenum silicidenitride oxide film with a molybdenum silicide target in a mixed gasatmosphere of an argon gas, an oxygen gas and a nitrogen gas.

The mixed gas preferably includes 65-79% argon gas, 8-24% oxygen gas,and 3-20% nitrogen gas by volume.

The step of forming the phase shifter film preferably includes the stepof forming a chromium oxide film with a chromium target in a mixed gasatmosphere of argon and oxygen.

The mixed gas includes 36-97% argon gas, and an oxygen gas of theremaining percent by volume.

The step of forming the phase shifter film preferably includes the stepof forming a chromium nitride film with a chromium target in a mixed gasatmosphere of argon, oxygen and nitrogen.

The mixed gas preferably includes 48-90% argon gas, 1-39% oxygen, and6-14% nitrogen by volume.

The step of forming the phase shifter film preferably includes the stepof forming a chromium nitride oxide film with a chromium target in amixed gas atmosphere of argon and nitrogen monoxide.

The mixed gas includes 82-87% argon gas, and nitrogen monoxide of theremaining percent by volume.

The step of forming the phase shifter film preferably includes the stepof forming a chromium carbide nitride oxide film with a chromium targetin a mixed gas atmosphere of argon, oxygen and methane.

The mixed gas preferably includes 78-88% argon gas, 2-13% oxygen, and8-10% methane by volume.

The step of forming the phase shift mask preferably includes the step offorming an antistatic film.

The step of forming the antistatic film preferably includes the step offorming a molybdenum film by a sputtering method between the steps offorming the phase shifter film and forming the resist film.

The step of forming the antistatic film preferably includes the step offorming a chromium film by a sputtering method between the steps offorming the phase shifter film and forming the resist film.

The step of etching the phase shifter film is preferably performed by adry etching method with a mixed gas of carbon fluoride and oxygen.

The step of etching the phase shifter film is preferably performed by adry etching method with a gas selected from the group consisting of amixed gas of methylene chloride and oxygen, a mixed gas of chlorine andoxygen, and a chlorine gas.

The step of forming the phase shifter film preferably includes the stepof performing heating process at or above 200° C. after forming thephase shifter film by a sputtering method.

As described above, in the phase shift mask and the manufacturing methodthereof in accordance with the present invention, the second lighttransmit portion is formed of a single material film.

In the manufacturing process of the phase shifter, a film of aprescribed single material is formed on a substrate transmittingexposure light by a sputtering method, and thereafter, a second lighttransmit portion is formed by prescribed etching.

This enables formation of a phase shift portion with a conventionalsputtering device, and also enables etching of a phase shifter portionwith a single etching agent.

Consequently, the steps of forming a phase shifter film and etching thesame are required only once, respectively, in the manufacturing process,so that probabilities of defects and of process errors in the patterndimension can be reduced, and thus a phase shift mask of high qualitycan be provided.

In addition, since a second light transmit portion is formed of a singlematerial film, a defective portion can be readily repaired by aconventional method.

The exposure method using the phase shift mask according to the presentinvention includes the following steps.

First, a resist film is applied onto a pattern formation layer. Then,the resist film is exposed using a phase shift mask having a phase shiftpattern having a first light transmit portion formed on a substratetransmitting exposure light having the substrate exposed, and a secondlight transmit portion of a single material having a phase oftransmitted exposure light converted by 180° with respect to the phaseof exposure light transmitted through the first light transmit portion,and having the transmittance of 5-40%.

As a result, it is possible to form a thin second light transmit portionof the thickness of approximately 1500Å to 2000Å, and to convert thephase of oblique exposure light by 180°. Therefore, exposure light hasits phase uniformed after transmitting through the second light transmitportion of the phase shift mask, making it possible to prevent occurrentof exposure failure. Consequently, the yield can be improved in themanufacturing steps of a semiconductor device.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a phase shift mask in a firstembodiment according to the present invention.

FIG. 2A is a cross sectional view of a phase shift mask according to thepresent invention. FIG. 2B is a schematic diagram showing an electricfield of exposure light on the mask. FIG. 2C is a schematic diagramshowing light intensity on a wafer.

FIGS. 3 to 6 are cross sectional views showing the first to fourth stepsof the manufacturing method of the phase shift mask in the firstembodiment according to the present invention.

FIG. 7 is a schematic diagram showing the structure of a DC magnetronsputtering apparatus.

FIG. 8 is a graph showing the relation of n value, k value and a filmthickness in using a krF laser.

FIG. 9 is a graph showing the relation of n value, k value and a filmthickness in using an i-line.

FIG. 10 is a graph showing the relation of n value, k value and a filmthickness in using a g-line.

FIG. 11 is a plot showing case by case a flow ratio of a mixed gas information of the phase shifter film in the first embodiment.

FIGS. 12 to 15 are cross sectional views showing the first to fourthsteps of the manufacturing method of a phase shift mask in a secondembodiment according to the present invention.

FIG. 16 is a graph showing the relation of n value, k value and a filmthickness in using an i-line.

FIG. 17 is a graph showing the relation of n value, k value and a filmthickness in using a g-line.

FIG. 18 is a first diagram plotting case by case a flow ratio of a mixedgas in formation of the phase shifter film in the second embodiment.

FIG. 19 is a second diagram plotting case by case a flow ratio of amixed gas in formation of the phase shifter film in the secondembodiment.

FIG. 20 is a third diagram plotting case by case a flow ratio of a mixedgas in formation of the phase shifter film in the second embodiment.

FIGS. 21 to 25 are cross sectional views showing the first to fifthsteps of the manufacturing method of a phase shift mask in a thirdembodiment according to the present invention.

FIG. 26 is a cross sectional view showing a defect repairing method of aphase shift mask according to the present invention.

FIG. 27 is a schematic diagram showing a state of an exposure methodusing the phase shift mask according to the present invention.

FIG. 28 is a graph showing the relationship between focus offset andcontact hole size in the exposure method using the phase shift maskaccording to the present invention.

FIG. 29 is a graph showing the relationship between focus offset andcontact hole size in the exposure method using a photomask in aconventional technique.

FIG. 30 is a graph showing a comparison of the relationship betweencoherence and depth of focus of the exposure method using the phaseshift mask according to the present invention with that of the exposuremethod using a phase shift mask in a conventional technique.

FIG. 31A is a cross sectional view of a photomask in a conventionaltechnique. FIG. 31B is a schematic diagram showing an electric field ofexposure light on the mask. FIG. 31C is a schematic diagram showinglight intensity on a wafer.

FIG. 32A is a cross sectional view of a phase shift mask in aconventional technique. FIG. 32B is a schematic diagram showing anelectric field of exposure light on the mask. FIG. 32C is a schematicdiagram showing light intensity on a wafer.

FIG. 33A is a cross sectional view of a phase shift mask in aconventional technique. FIG. 33B is a schematic diagram showing anelectric field of exposure light on the mask. FIG. 33C is a schematicdiagram showing light intensity on a wafer.

FIG. 34 is a graph showing the relation between a transmittance ofexposure light and a thickness of a resist film.

FIGS. 35 to 39 are cross sectional views showing the first to fifthsteps of a manufacturing method of a phase shift mask in a conventionaltechnique.

FIG. 40 is a cross sectional view showing a problem of the phase shiftmask in the conventional technique.

FIG. 41 is a diagram showing a problem of the exposure method using aphase shift mask in a conventional technique.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment in accordance with the present invention willhereinafter be described.

First, description will be made of the structure of phase shift mask inthis embodiment with reference to FIG. 1. A phase shift mask 200includes a quartz substrate 1 transmitting exposure light, and a phaseshift pattern 30 formed on a main surface of quartz substrate 1. Phaseshift pattern 30 includes a first light transmit portion 10 havingquartz substrate i exposed, and a second light transmit portion 4 of asingle material having a phase of transmitted exposure light convertedby 180° with respect to the phase of exposure light transmitted throughfirst light transmit portion 10, and having the transmittance of 5-40%.

Description will be made of an electric field of exposure light passingtherethrough on phase shift mask 200 of the above structure, and lightintensity on a wafer with reference to FIGS. 2A, 2B, 2C.

FIG. 2A is a cross sectional view of phase shift mask 200 describedabove. Referring to FIG. 2B, since the electric field on the mask isinverted at an edge of a exposure pattern, the electric field at theedge portion of the exposure pattern is invariably zero. Accordingly, asshown in FIG. 2C, the difference in the electric field on the wafer atlight transmit portion 10 and at phase shift portion 4 of the exposurepattern is sufficient for obtaining higher resolution.

It should be noticed that the transmittance of second light transmitportion 4 is set to 5-40% for the purpose of adjusting the thickness ofa resist film after development to adapt appropriately the exposureamount for lithography.

Description will now be made of a manufacturing method of phase shiftmask 200 in a second embodiment, employing a molybdenum silicide oxidefilm or a molybdenum silicide nitride oxide film as a phase shifterfilm.

FIGS. 3 to 6 are cross sectional views showing the manufacturing processof phase shift mask 200 shown in FIG. 1.

Referring to FIG. 3, on a quartz substrate 1 formed is a phase shifterfilm 4 of a molybdenum silicide oxide film or a molybdenum silicidenitride oxide film by a sputtering method.

Thereafter, in order to stabilize the transmittance of phase shifterfilm 4, heating process is performed at or above 200° C. using a cleanoven or the like.

Consequently, fluctuation of the transmittance (0.5-1.0%) conventionallycaused by heating process such as resist application process(approximately 180° C.) in formation of a phase shifter film can beprevented.

Subsequently, an electron beam resist film 5 (EP-810S (registeredtrademark) manufactured by Nihon Zeon) of approximately 5000Å inthickness is formed on phase shifter film 4. Since the molybdenumsilicide oxide film or molybdenum silicide nitride oxide film does nothave conductivity, an antistatic film 6 (Espacer 100 (registeredtrademark) manufactured by Showa Denko) of approximately 100Å is formedthereon for prevention of being charged in irradiation of electronbeams.

Referring to FIG. 4, electron beam resist film 5 is irradiated withelectron beams, and thereafter, antistatic film 6 is washed away withwater. Resist film 5 having a prescribed resist pattern is then formedby development of resist film 5.

Referring to FIG. 5, phase shifter film 4 is etched with resist film 5as a mask. At this time, an RF ion etching apparatus of horizontal flatplate type is employed, which performs etching for approximately elevenminutes under the conditions of the electrode-substrate distance of 60mm, the operating pressure of 0.3 Torr, and the flow rates of reactiongases CF₄ and O₂ of 95 sccm and 5 sccm, respectively.

Referring to FIG. 6, resist 5 is removed. Through these steps, the phaseshift mask in accordance with the present embodiment is completed.

Formation of the phase shifter film utilizing the above-describedsputtering method will hereinafter be described in detail. To have thetransmittance for exposure light within the range of 5-40%, and toconvert a phase of exposure light by 180° are the requirements for aphase shift film.

As a film satisfying these conditions, therefore, a film made of amolybdenum silicide nitride oxide was employed in the presentembodiment.

Description will be made of a sputtering apparatus for forming theaforementioned film with reference to FIG. 7.

FIG. 7 is a schematic diagram showing the structure of a DC magnetronsputtering apparatus 500.

DC magnetron sputtering apparatus 500 includes a vacuum vessel 506provided with a magnetron cathode 509 including a target 507 and amagnet 508 therein.

An anode 510 is provided opposed to and spaced by a predetermineddistance from target 507, on the opposite surface of which from target507 provided is a quartz substrate 1 of 2.3 mm in thickness and 127 mmsquare, for example.

An exhaust pipe 512 and a gas feed pipe 513 are provided atpredetermined positions of vacuum vessel 506. In formation of a film,molybdenum silicide is used as a target, and the temperature of quartzsubstrate 1 is held at 60°-150° C. by a heater and a temperaturecontroller, not shown.

Under these conditions, argon as a sputter gas and a mixed gas of oxygenand nitrogen as a reaction gas are introduced from gas feed pipe 513 ata prescribed rate, the pressure in vacuum vessel 506 is held at aprescribed value, and a direct current voltage is applied betweenelectrodes.

In this embodiment, phase shifter films of a molybdenum silicide oxideand of a molybdenum silicide nitride oxide were formed in variousconditions.

Table 1 shows the pressure in vacuum vessel 506, the deposition rate andthe film material in each of the cases in which various flow ratios ofthe mixed gas are set. A phase shifter film of a molybdenum silicidenitride oxide is to be formed in Cases M-1 to M-7, M-14, and M-15, whilea phase shifter film of a molybdenum silicide oxide is to be formed inCases M-8 to M-13, M-16, and M-17.

Tables 2-4 are graphs showing the transmittance, the n value and the kvalue in an optical constant (n-i·k), and the film thickness d_(s) forconverting a phase of exposure light by 180°, in the cases employing akrF laser (λ=248 nm), an i-line (λ=365 nm) and a g-line (λ=436 nm) asexposure light, respectively.

In Tables 2-4, the film thickness d_(s) can be obtained from thefollowing:

    d.sub.s =λ/2(n-1)                                   (2)

where λ is a wavelength of exposure light, and n is a value in theoptical constant.

                  TABLE 1                                                         ______________________________________                                        gas flow ratio             depositi                                           %             pressure × 10.sup.-3                                                                 on rate  film                                      case Ar     O.sub.2                                                                              N.sub.2                                                                            Torr       Å/min                                                                            material                            ______________________________________                                        M-1  72.6   23.8   3.6  2.0        709    MoSi                                M-2  77.1   18.3   4.6  2.0        645    nitride                             M-3  72.1   8.6    19.3 2.0        600    oxide                               M-4  68.6   7.9    23.5 2.1        525    film                                M-5  61.4   7.0    31.6 2.1        486                                        M-6  57.4   13.1   29.5 2.2        522                                        M-7  65.4   17.8   16.8 2.0        578                                        M-8  79.5   20.5   0    2.0        635    MoSi                                M-9  73.3   26.7   0    2.0        600    oxide                               M-10 78.8   21.2   0    2.6        225    film                                M-11 81.1   18.9   0    2.6        632                                        M-12 82.3   17.7   0    2.6        650                                        M-13 83.5   16.5   0    2.6        754                                        M-14 73.4   14.9   11.7 3.0        702    MoSi                                M-15 79.0   16.8   4.2  2.8        750    nitride                                                                       oxide                                                                         film                                M-16 76.0   24.0   0    2.6        830    MoSi                                M-17 92.0   8.0    0    5.5        487    oxide                                                                         film                                ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        krF laser (wavelength 248 nm)                                                  ##STR1##                                                                                     ##STR2##                                                                                   ##STR3##                                         case   %           n       k      Å                                       ______________________________________                                        M-1    5.22        1.195   0.409  1355                                        M-2    3.59        1.860   0.437  1442                                        M-3    2.92        1.986   0.530  1258                                        M-4    0.69        2.14    0.868  1088                                        M-5    0.74        2.09    0.821  1137                                        M-6    1.8         1.922   0.569  1345                                        M-7    2.6         1.963   0.538  1288                                        M-8    7.0         1.79    0.318  1570                                        M-9    4.6         1.68    0.322  1824                                        M-10   10.2        1.730   0.251  1700                                        M-11   5.0         1.76    0.350  1630                                        M-12   6.13        1.91    0.384  1360                                        M-13   5.51        1.90    0.394  1380                                        M-14   3.52        2.054   0.5325 1176                                        M-15   3.03        2.111   0.5855 1116                                        M-16   4.39        1.804   0.3844 1541                                        M-17   6.88        1.842   0.3409 1472                                        ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                        i-line (wavelength 365 nm)                                                     ##STR4##                                                                                     ##STR5##                                                                                   ##STR6##                                         case   %           n       k      Å                                       ______________________________________                                        M-1    11.6        1.874   0.280  2088                                        M-2    11.5        1.950   0.304  1921                                        M-3    8.82        2.11    0.397  1644                                        M-4    2.9         2.318   0.697  1382                                        M-5    4.15        2.344   0.626  1362                                        M-6    3.5         2.01    0.511  1807                                        M-7    4.53        1.88    0.414  2074                                        M-8    44.5        2.11    0.118  1644                                        M-9    78.6        1.85    0.0169 2147                                        M-10   73.8        1.77    0.020  2370                                        M-11   18.7        1.91    0.222  2005                                        M-12   12.2        1.81    0.254  2250                                        M-13   17.9        1.98    0.245  1860                                        M-14   8.55        2.068   0.389  1709                                        M-15   8.71        2.189   0.420  1535                                        M-16   9.39        1.707   0.2536 2581                                        M-17   16.5        1.833   0.2207 2192                                        ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                        g-line (wavelength 436 nm)                                                     ##STR7##                                                                                     ##STR8##                                                                                   ##STR9##                                         case   %           n       k      Å                                       ______________________________________                                        M-1    12.0        1.786   0.249  2774                                        M-2    16.4        2.006   0.265  2167                                        M-3    11.7        2.148   0.358  1900                                        M-4    3.9         2.346   0.644  1620                                        M-5    3.4         2.121   0.572  1945                                        M-6    4.4         1.860   0.410  2535                                        M-7    8.8         2.018   0.367  2141                                        M-8    46.3        2.197   0.114  1821                                        M-9    83.0        1.795   0.0069 2742                                        M-10   78.0        1.733   0.0123 2974                                        M-11   22.2        1.901   0.195  2420                                        M-12   21.1        1.982   0.220  2220                                        M-13   13.3        1.702   0.213  3105                                        M-14   13.0        2.124   0.3325 1940                                        M-15   11.9        2.185   0.3653 1840                                        M-16   17.9        1.886   0.222  2460                                        M-17   18.2        1.775   1.1934 2812                                        ______________________________________                                    

FIGS. 8 to 10 are graphs of data shown in Table 2 to respectively, inwhich the horizontal axis indicates the n value in the optical constant,the left vertical axis indicates the k value in the optical constant,and the right vertical axis indicates the film thickness d_(s).

The transmittance T is also shown in FIG. 8 to 10.

Referring to FIG. 8 showing the cases of exposure light of the krFlaser, it can be seen that the transmittance T within the range of 5-40%required for a phase shifter film is obtained in M-1, M-8, M-10 to M-13,and M-17.

Referring to FIG. 9 showing the cases of exposure light of the i-line,the transmittance T within the range of 5-40% required for a phase shiftmask is obtained in M-1 to M-3, M-8, and M-11 to M-17.

Referring to FIG. 10 showing the cases of exposure light of the g-line,it can be seen that the transmittance T within the range of 5-40%required for a phase shifter film is obtained in M-1 to M-3, M-7, andM-11 to M-17.

As a result, the films formed in M-1 to M-3, M-7, M-8, and M-11 to M-17can be employed as a phase shifter film.

FIG. 11 is a graph showing the above cases with respect to gas flowratios. In the graph shown in FIG. 11, respective rates of argon, oxygenand nitrogen in Cases M-1 to M-17 are described.

In this graph, a point of a mixed gas in each case is plotted, whereinthe base of the triangle indicates the flow ratio (%) of argon, the leftoblique side thereof indicates the flow ratio (%) of oxygen, and theright oblique side thereof indicates the flow ratio (%) of nitrogen. Inaccordance with the result shown in FIGS. 8 to 10, a case the film ofwhich is applicable as a phase shifter film is indicated by a circle,while a case the film of which is not applicable to a phase shifter filmis indicated by a cross.

As can be seen from the graph in FIG. 11, a mixed gas for forming amolybdenum silicide oxide film applicable as a phase shifter filmincludes 76-92% argon and 18-24% oxygen by volume.

A mixed gas for forming a molybdenum silicide nitride oxide filmapplicable as a phase shifter film includes 65-79% argon, 8-24% oxygen,and 3-20% nitrogen by volume.

The upper limit of oxygen is set to 35%, because the rate occupied byoxygen of 50% or more will cause deposition of an oxide on an electrodein the sputtering apparatus, thereby preventing sputtering. It is thusdefined by the restriction of the apparatus.

As described above, in the phase shift mask in accordance with thepresent invention, a second light transmit portion is constituted onlyof a molybdenum silicide oxide film or a molybdenum silicide nitrideoxide film having the transmittance of 4-50%.

In the manufacturing process thereof, a molybdenum silicide oxide or amolybdenum silicide nitride oxide is formed to a prescribed filmthickness by a sputtering method, and thereafter, a prescribed etchingis performed, whereby the second light transmit portion is formed.

Consequently, a phase shifter film can be formed with a conventionalsputtering apparatus, and additionally, probabilities of defects anderrors in a pattern dimension can be reduced because etching process isrequired only once.

Description will hereinafter be made of a method of manufacturing phaseshift mask 200 in accordance with a third embodiment, where either of achromium oxide film, a chromium nitride oxide film, and a chromiumcarbide nitride oxide film is employed as a phase shifter film.

FIGS. 12 to 15 are cross sectional views showing the manufacturing stepsof phase shift mask 200 shown in FIG. 1.

Referring to FIG. 12, phase shifter film 4 of a chromium oxide film, achromium nitride oxide film, or a chromium carbide nitride oxide isformed on quartz substrate 1 by a sputtering method.

In order to stabilize the transmittance of phase shifter film 4, heatingprocess is performed at approximately 200° C. or more with a clean ovenor the like.

This prevents fluctuation of the transmittance (0.51-1.0%) caused byconventional heating processing (approximately 180° C.) in resistapplication process after phase shifter film formation.

Subsequently, a resist film 5 of approximately 5000Å in thickness isformed on phase shifter film 4.

Referring to FIG. 13, resist film 5 is irradiated with an i-line anddeveloped so as to have a prescribed resist pattern.

Referring to FIG. 14, phase shifter film 4 is etched with resist film 5as a mask. At this time, an RF ion etching apparatus of horizontal flatplate type is employed, in which etching is performed for approximatelyfour minutes under the conditions of the electrodesubstrate distance of100 mm, the operating pressure of 0.3 Torr, the flow rates of reactiongases CH₂ Cl₂ and O₂ of 25 sccm and 75 sccm, respectively. The phaseshift mask in accordance with the present embodiment is thus completed.

Detailed description will now be made of formation of the phase shiftmask utilizing the sputtering method described above. To have thetransmittance within the range of 5-40% for exposure light, and toconvert of a phase of exposure light by 180° are the requirements for aphase shifter film.

As a film satisfying these conditions, therefore, a film made of achromium oxide, a chromium nitride oxide, or a chromium carbide oxidenitride is employed in the present embodiment.

The structure of the sputtering apparatus for forming the above phaseshifter film is the same as that shown in FIG. 7, and the descriptionthereof is not repeated.

In the present embodiment, phase shift masks of a chromium oxide film, achromium nitride oxide film, and a chromium carbide nitride oxide filmwere formed in various cases.

Table 5 shows the pressure in vacuum vessel 506, the deposition rate andthe film material in each of the cases in which various flow ratios of amixed gas are set. A phase shifter film of a chromium oxide is to beformed in Cases C-1 to C-13, a phase shifter film of a chromium nitrideoxide is to be formed in Cases C-14 to C-26, and a phase shifter film ofa chromium carbide nitride oxide is to be formed in Cases C-27 to C-30.

Tables 6 to 8 are graphs showing the transmittance, the n value and thek value in the optical constant (n-i·k), and the film thickness d_(s)for converting a phase of exposure light by 180° in the cases employinga krF laser (λ=248 nm), an i-line (λ=365 nm) and a g-line (λ=436 nm),respectively.

In Tables 6 to 8, the film thickness d_(s) can be obtained from thefollowing:

    d.sub.s =λ/2(n=1)                                   (2)

where λ is a wavelength of exposure light, and n is a value in theoptical constant.

                  TABLE 5                                                         ______________________________________                                                            pres-                                                     gas flow ratio      sure ×                                                                          depositi film                                     %                   10.sup.-3                                                                             on rate  ma-                                      case Ar     O.sub.2                                                                              N.sub.2                                                                            NO   CH.sub.4                                                                           Torr  Å/min                                                                            terial                         ______________________________________                                        C-1  71.4   28.6   0    0    0    3.0   259    Cr                             C-2  92.3   7.7    0    0    0    3.9   850    oxide                          C-3  90.0   10.0   0    0    0    3.0   900    film                           C-4  85.0   15.0   0    0    0    2.0   941                                   C-5  85.5   14.5   0    0    0    6.1   796                                   C-6  89.3   10.7   0    0    0    8.0   828                                   C-7  92.7   7.3    0    0    0    4.0   758                                   C-8  96.6   3.4    0    0    0    4.0   448                                   C-9  94.8   5.2    0    0    0    8.1   733                                   C-10 93.1   6.9    0    0    0    6.1   791                                   C-11 90.2   9.81   0    0    0    4.0   824                                   C-12 90.1   9.93   0    0    0    4.1   787                                   C-13 95.1   4.92   0    0    0    8.2   659                                   C-14 54.1   32.4   13.5 0    0    1.5   110    Cr                             C-15 48.8   39.0   12.2 0    0    1.5   108    nitride                        C-16 87.2   6.4    6.4  0    0    4.1   592    oxide                          C-17 82.9   4.9    12.2 0    0    4.2   523    film                           C-18 90.0   1.3    8.7  0    0    4.1   756                                   C-19 76.0   0      0    24.0 0    2.0   600                                   C-20 83.0   0      0    17.0 0    3.2   620                                   C-21 75.5   0      0    24.5 0    2.3   570                                   C-22 86.0   0      0    14.0 0    4.2   550                                   C-23 86.5   0      0    13.5 0    4.1   580                                   C-24 82.4   0      0    17.6 0    3.2   520                                   C-25 86.2   0      0    13.8 0    4.2   129                                   C-26 87.1   0      0    12.9 0    4.1   675                                   C-27 85.2   5.3    0    0    9.5  4.0   471    Cr                             C-28 82.9   7.9    0    0    9.2  3.0   513    carbide                        C-29 78.3   13.0   0    0    8.7  2.0   642    nitride                        C-30 87.9   2.3    0    0    9.8  8.1   399    oxide                                                                         film                           ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                        krF laser (wavelength 248 nm)                                                  ##STR10##                                                                                   ##STR11##                                                                                   ##STR12##                                        case  %           n        k      Å                                       ______________________________________                                        C-1   8.9         2.782    0.5696 696                                         C-13  3.50        2.538    0.7448 806.2                                       C-25  3.80        7.565    0.7347 792                                         ______________________________________                                    

                  TABLE 7                                                         ______________________________________                                        i-line (wavelength 365 nm)                                                     ##STR13##                                                                                   ##STR14##                                                                                   ##STR15##                                        case  %           n        k      Å                                       ______________________________________                                        C-1   31.7        2.23     0.187  1484                                        C-2   8.95        2.529    0.5108 1194                                        C-3   6.08        2.355    0.5495 1347                                        C-4   6.52        2.481    0.5749 1212                                        C-5   5.81        2.258    0.5252 1451                                        C-6   5.64        2.272    0.5364 1435                                        C-7   6.18        2.275    0.5186 1432                                        C-8   6.22        2.225    0.5000 1490                                        C-9   12.9        2.513    0.4171 1238                                        C-10  8.52        2.296    1.4603 1408                                        C-11  6.63        2.238    0.4922 1474                                        C-12  7.23        2.299    0.8949 1405                                        C-13  11.3        2.579    0.4634 1159                                        C-14  9.79        2.44     0.468  1267                                        C-15  10.0        2.50     0.476  1217                                        C-16  5.35        2.527    0.6365 1195                                        C-17  4.65        2.494    0.6588 1222                                        C-18  8.78        2.632    0.5399 1118                                        C-19  0.199       2.142    1.098  1599                                        C-20  0.543       2.283    1.089  1250                                        C-21  1.42        2.316    0.8407 1387                                        C-22  1.60        2.346    0.8336 1100                                        C-23  0.102       2.290    1.3672 1415                                        C-24  1.38        2.413    0.9021 1100                                        C-25  12.1        2.471    0.4257 1241                                        C-26  1.80        2.505    0.8904 1213                                        C-27  6.18        2.530    0.6010 1196                                        C-28  5.06        2.283    0.5625 1422                                        C-29  3.47        2.440    0.7066 1267                                        C-30  8.65        2.413    0.4894 1291                                        ______________________________________                                    

                  TABLE 8                                                         ______________________________________                                        g-line (wavelength 436 nm)                                                     ##STR16##                                                                                   ##STR17##                                                                                   ##STR18##                                        case  %           n        k      Å                                       ______________________________________                                        C-2   19.58       2.660    0.3262 1313                                        C-3   14.2        2.365    0.3689 1597                                        C-4   11.1        2.285    0.4029 1696                                        C-5   17.3        2.595    0.3495 1411                                        C-6   16.1        2.538    0.3669 1417                                        C-7   19.73       2.629    0.3220 1338                                        C-8   21.9        2.630    0.2936 1537                                        C-9   27.1        2.590    0.2343 1371                                        C-10  25.3        2.900    0.2514 1147                                        C-11  21.2        2.539    0.297  1416                                        C-12  20.8        2.617    0.3062 1348                                        C-13  21.4        2.676    0.2760 1301                                        C-16  14.4        2.786    0.4263 1221                                        C-17  12.5        2.732    0.4621 1258                                        C-18  9.94        2.053    0.3587 2070                                        C-19  1.93        2.607    0.925  1356                                        C-21  2.84        2.706    0.8715 1270                                        C-22  6.13        2.706    0.6562 1280                                        C-23  3.60        2.631    0.7820 1320                                        C-24  5.02        2.748    0.7250 1250                                        C-26  3.98        2.630    0.7475 1337                                        C-27  1.29        1.731    0.4952 2982                                        C-28  14.5        2.482    0.3834 1471                                        C-29  5.50        2.335    0.5641 1633                                        C-30  18.8        2.580    0.3304 1380                                        ______________________________________                                    

FIGS. 16 and 17 are graphs; of data shown in Tables 7 and 8. Thehorizontal axis indicates the n value in the optical constant, the leftvertical axis indicates the k value in the optical constant, and theright vertical axis indicates the film thickness d_(s).

The transmittance T is also shown in FIGS. 16 and 17.

Referring to FIG. 16 showing the case of exposure light of the i-line,it can be seen that the transmittance T within the range of 5-40%required for a phase shift mask is obtained in C-1 to C-16, C-18, C-25,C-27, C-28, and C-30.

Referring to FIG. 17 showing the case of exposure light of the g-line,it can be seen that the transmittance T within the range of 5-40%required for a phase shift mask is obtained in Cases C-2 to C-13, C-16to C-18, C-22, C-24, and C-28 to C-30.

As a result, the films formed in Cases C-1 to C-18, C-22, C-24, C-25,and C-27 to C-30 can be employed as a phase shifter film.

FIGS. 18 to 20 are graphs showing the above cases based on the relationof gas flow ratios in mixed gases Ar+O₂, Ar+O₂ +N₂, Ar+NO, and Ar+O₂+CH₄, respectively.

The graph of FIG. 18 shows the rates of argon, oxygen and nitrogen inCases C-1 to C-18.

In this graph, a point of a mixed gas in each case is plotted, whereinthe base of the triangle indicates the flow ratio (%) of argon, the leftoblique side of the triangle indicates the flow ratio (%) of oxygen, andthe. right oblique side of the triangle indicates the flow ratio (%) ofnitrogen.

In accordance with the result in FIGS. 16 and 17, a case the film ofwhich is applicable as a phase shifter film is indicated by a circle,while a case the film of which is not applicable as a phase shifter filmis indicated by a cross.

As can be seen from the graph of FIG. 18, a mixed gas for forming achromium oxide film applicable as a phase shifter film includes 36-97%argon and 3-64% oxygen by volume.

A mixed gas for forming a chromium nitride oxide film applicable as aphase shifter film includes 48-90% argon, 1-39% oxygen, and 6-14%nitrogen by volume.

The upper limit of oxygen is set to 39%, because the rate occupied byoxygen of 50% or more will cause deposition of an oxide on an electrodein the sputtering apparatus, thereby preventing sputtering. It is thusdefined by the restriction of the apparatus.

FIG. 19 is a graph showing the rates of argon and NO in Cases C-19 toC-26. In accordance with the results in FIGS. 16 and 17, a case the filmof which is applicable as a phase shift mask is indicated by a circle,while a case the film of which is not applicable as a phase shifter maskis indicated by a cross.

FIG. 20 is a graph showing the rates of argon, oxygen and methane inCases C-27 to C-30.

In the graph, a point of a mixed gas in each case is plotted, whereinthe base of the triangle indicates the flow ratio (%) of argon, the leftoblique side thereof indicates the flow ratio (%) of oxygen, and thelight oblique side thereof indicates the flow ratio (%) of methane.

In accordance with the result in FIGS. 16 and 17, a case the film ofwhich is applicable as a phase shifter film is indicated by a circle,while a case the film of which is not applicable as a phase shifter filmis indicated by a cross.

As can be seen from the graphs in FIGS. 19 and 20, a mixed gas forforming a chromium nitride oxide film applicable as a phase shifter filmincludes 82-87%.argon, and 13-18% nitrogen monoxide by volume.

A mixed gas for forming a chromium carbide nitride oxide film applicableas a phase shifter film includes 78-88% argon, 2-13% oxygen, and 8-10%methane by volume.

As described above, in the phase shift mask in accordance with thepresent embodiment, a second light transmit portion is constituted onlyof a film of a chromium oxide, a chromium nitride oxide, or a chromiumcarbide nitride oxide, having the transmittance of 4-50%.

In the manufacturing process thereof, a film of a chromium oxide, achromium nitride oxide, or a chromium carbide nitride oxide is formed toa prescribed film thickness by a sputtering method, and thereafter, aprescribed etching is performed, so that the second light transmitportion is formed.

Consequently, a phase shifter film can be formed with a conventionalsputtering apparatus, and probabilities of defects and errors in apattern dimension can be reduced since etching process is required onlyonce.

Although an oxide and a nitride oxide of molybdenum silicide, and anoxide, a nitride oxide, and a carbide nitride oxide of chromium are usedas the second light transmit portion in the second and thirdembodiments, it is not limited to them, and an oxide and a nitride ofmetal, and an oxide and a nitride oxide of metal silicide may be used.

Description will now be made of a fourth embodiment in accordance withthe present invention. In the present embodiment, an antistatic metalfilm is formed for prevention of being charged in irradiation ofelectron beams or laser beams on a phase shifter film in themanufacturing process thereof.

The manufacturing process of the phase shifter film will be describedwith reference to FIGS. 21 to 25.

FIGS. 21 to 25 are cross sectional views corresponding to the crosssectional structure of the phase shift mask shown in FIG. 1.

Referring to the figures, as in the second and third embodiments, phaseshifter film 4 is formed on quartz substrate, which is made of amolybdenum silicide oxide film, a molybdenum silicide nitride oxidefilm, a chromium oxide film, a chromium nitride oxide film, or achromium carbide nitride oxide film.

Thereafter, an antistatic film 6 of approximately 100-500Å in thicknessis formed on phase shifter film 4. When the film material of the phaseshifter film belongs to the Mo family, a molybdenum film is to be formedas antistatic film 6. When it belongs to the Cr family, a chromium filmis to be formed as antistatic film.

This is because phase shifter film 4 of a molybdenum silicide oxide, amolybdenum silicide nitride oxide, a chromium oxide, a chromium nitrideoxide, or a chromium carbide nitride oxide, formed in the aforementionedmethod does not have conductivity.

With regard to Cases C-1 to C-3 described in connection with the thirdembodiment, since a chromium oxide film formed in the above cases hasconductivity, the antistatic film is not required.

Subsequently, an electron beam resist film of approximately 5000Å inthickness is formed on antistatic film 6.

Referring to FIG. 22, resist film 5 having a desired resist pattern isformed by exposing to electron beams and developing a prescribed portionof electron beam resist film 5.

Referring to FIG. 23, sequential dry etching of antistatic film 6 andphase shifter film 4 is performed using a CF₄ +O₂ gas, with electronbeam resist film 5 as a mask when antistatic film 6 belongs to the Mofamily.

Referring to FIG. 24, resist film 5 is removed using O₂ plasma or thelike. Referring to FIG. 25, antistatic film 6 is removed by etching withetching liquid (a mixture of ammonium ceric nitrate and perchloric acid)or the like.

The phase shift mask is thus completed.

Referring to FIG. 23 again, when antistatic film 6 belongs to the Crfamily, sequential dry etching of antistatic film 6 and phase shifterfilm 4 is performed with a CH₂ Cl₂ +O₂ gas, a Cl₂ +O₂ gas, or Cl₂ gas,with electron beam resist film 5 as a mask.

Referring to FIG. 24, resist film 5 is removed using O₂ plasma or thelike. Referring to FIG. 25, antistatic film 6 is removed by etching withsulfuric acid.

The phase shift mask is thus completed.

Although an antistatic film of molybdenum is formed in the case of aphase shift mask belonging to the Mo family, and an antistatic film ofchromium is formed in the case of a phase shift mask belonging to the Crfamily in etching of the phase shift mask, the present invention is notto limited to this, and the same effects can be obtained by using anantistatic film of Mo for a phase shift mask belonging to the Cr family,or using an antistatic film belonging to the Cr family for a phaseshifter film belonging to the Mo family.

As described above, providing a molybdenum film in the manufacturingprocess of the phase shift mask, an antistatic effect in irradiation oflight beams can be obtained. This also serves as a light reflecting filmfor a position detector of optical type.

Although a molybdenum film or a chromium film is used as an antistaticfilm in the fourth embodiment, the same effects can be obtained by usinga film of W, Ta, Ti, Si, Al or the like, or alloys thereof.

Description will be now made of methods of detecting a defect andrepairing the same, when a remaining defect (an opaque defect) 50 or apin hole defect (a clear defect) 51 occurs on the phase shift maskformed in the first to third embodiments, as shown in FIG. 26.

First, utilizing a light transmit type defect detection apparatus(manufactured by KLA, 239HR type), the presence of a defect in amanufactured phase shift mask is checked by comparing chips.

In this defect detection apparatus, the check is carried out with lightemitted from a mercury lamp.

As a result, a remaining defect in which the phase shifter film remainson the pattern to be etched, and a pin hole defect in which the phaseshifter film to be left is eliminated because of a pin hole or a lackedshape are detected.

These defects are then repaired. The remaining defect is repaired by alaser blow repair apparatus with a YAG laser, as in a conventionalphotomask.

Another method of removing the remaining defect is to performassist-etching by FIB with a gas for sputter etching.

The pin hole defect is repaired by burying the pin hole defect portionthrough deposition of a carbon film 52 by FIB assist deposition method,as in a conventional photomask.

A good phase shift mask can thus be obtained without carbon film 52being peeled off even when the repaired phase shift mask is washed.

Description will now be made of an exposure method using theabove-described phase shift mask.

When the phase shift mask is used, a phase shifter film is formed withthe thickness of approximately 1500Å to 2000Å as shown in film thicknessdimension (ds) of Table 2 to Table 4 and Table 6 to Table 8. Since thephase shifter film is formed with the thickness approximately half ofthat of a conventional phase shifter film, it is possible to convertoblique exposure light included in exposure light by 180° as shown inFIG. 27.

As a result, as shown in FIG. 28, when a contact hole of 0.4 μm is to beopened, for example, it is possible to allow focus tolerance of 1.2 μm.In the case of a conventional photomask, as shown in FIG. 29, when acontact hole of 0.4 μm was to be opened, focus offset of only 0.6 μm wasallowed.

In an exposure apparatus having coherence of 0.3 to 0.7 favorably0.5-0.6, as shown in FIG. 30, it is possible to substantially improvedepth of focus as compared to the case of the conventional photomask.

FIGS. 28 and 29 show the relationship between contact hole size andfocus tolerance in the case where a reduction and projection exposureapparatus having a reduction ratio of 5:1 is used. However, it ispossible to obtain similar effects with a reduction and projectionexposure apparatus having a reduction ratio of 4:1 or 3:1, or projectionexposure apparatus having a reduction ratio of 1:1. It is possible toobtain similar effects not only with a projection exposure apparatus butalso with a contact exposure apparatus and a proximity exposureapparatus.

In addition, it is possible to obtain similar effects that a krF laser(λ=248 nm), an i-line (λ=365 nm) and a g-line (λ=436 nm) is using asexposure light.

As described above, according to the exposure method using the phaseshift mask in this embodiment, since it is possible to preventoccurrence of exposure failure, it is possible to improve the yield inthe manufacturing steps of a semiconductor device. The exposure methodcan be effectively used in the manufacturing steps of a semiconductordevice such as a DRAM of 4M, 16M, 64M, 256M, an SRAM, a flash memory, anASIC (Application Specific Integrated Circuit), a microcomputer, andGaAs. Furthermore, the exposure method can be well used in themanufacturing steps of a unitary semiconductor element and a liquidcrystal display.

In the phase shift mask in accordance with the present invention, asecond light transmit portion is made only of a single material film.

Additionally, in the manufacturing process of the phase shift film, thesecond light transmit portion is formed by forming a prescribed phaseshifter film on a substrate transmitting exposure light by a sputteringmethod, and thereafter, performing a prescribed etching.

This enables formation of a phase shifter film at a single step with aconventional sputtering apparatus. Moreover, since etching process isrequired only once, probabilities of defects and errors in the patterndimension will be decreased, so that a phase shift mask high quality canbe provided.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

What is claimed is:
 1. A method of manufacturing a phase shift mask,which method comprises:sputtering a phase shifter film of a prescribedthickness on a substrate, said phase shifter film consisting of a singlematerial having a phase of transmitted exposure light converted by 180°and having transmittance of 5% to 40%; forming a resist film having aprescribed pattern on the phase shifter film; and dry etching said phaseshifter film using the resist film as a mask to form a first lighttransmit portion having said substrate exposed and a second lighttransmit portion made of said phase shifter film;wherein said singlematerial is selected from the group consisting of an oxide of a metal, anitride oxide of a metal, an oxide of a metal silicide and a nitrideoxide of a metal silicide.
 2. The method according to claim 1,comprisingsputtering a phase shifter film of an oxide of molybdenumsilicide using a target of molybdenum silicide in a mixed gas atmosphereof argon and oxygen.
 3. The method according to claim 2, whereinsaidmixed gas includes 76 to 92% argon and oxygen of the remaining percentby volume.
 4. The method according to claim 2, comprisingdry etchingsaid phase shifter film with a mixed gas of carbon fluoride and oxygen.5. The method according to claim 1, comprisingsputtering a phase shifterfilm of a nitride oxide of molybdenum silicide using a target ofmolybdenum silicide in a mixed gas atmosphere of argon, oxygen andnitrogen.
 6. The method according to claim 5, whereinsaid mixed gasincludes 65 to 79% argon, 8 to 24% oxygen, and 3 to 20% nitrogen byvolume.
 7. The method according to claim 1, comprisingsputtering a phaseshifter film of an oxide of chromium using a target of chromium in amixed gas atmosphere of argon and oxygen.
 8. The method according toclaim 7, whereinsaid mixed gas includes 36 to 97% argon and oxygen ofthe remaining percent by volume.
 9. The method according to claim 7,comprisingdry etching said phase shifter film with a gas selected fromthe group consisting of a mixed gas of methylene chloride and oxygen, amixed gas of choline and oxygen, and a choline gas.
 10. The methodaccording to claim 1, comprisingsputtering a phase shifter film of anitride oxide of chromium using a target of chromium in a mixed gasatmosphere of argon, oxygen and nitrogen.
 11. The method according toclaim 10, whereinsaid mixed gas includes 48 to 90% argon, 1 to 39%oxygen, and 6 to 14% nitrogen by volume.
 12. The method according toclaim 1, comprisingsputtering a phase shifter film of a nitride oxide ofchromium using a target of chromium in a mixed gas atmosphere of argonand nitrogen monoxide.
 13. The method according to claim 12, whereinsaidmixed gas includes 82 to 87% argon, and nitrogen monoxide of theremaining percent by volume.
 14. The method according to claim 1,comprisingsputtering a phase shifter film of a carbide nitride oxide ofchromium using a target of chromium in a mixed gas atmosphere of argonoxygen and methane.
 15. The method according to claim 14, whereinsaidmixed gas includes 78 to 88% argon, 2 to 13% oxygen, and 8 to 10%methane by volume.
 16. The method according to claim 1,comprisingforming an antistatic film.
 17. The method according to claim16, comprisingsputtering a molybdenum antistatic film on said phaseshifter film before forming said resist film.
 18. The method accordingto claim 16, comprisingsputtering a chromium antistatic film on saidphase shifter film before forming said resist film.
 19. The methodaccording to claim 1, comprisingheat treating said sputtered phaseshifter film at or above 200° C.